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Project Notes

#409 Conehead

The Conehead is the fourth in a series of beautiful electronic bug boards from the Boldport Club, Project #24 April 2018. This one chirps in response to light.

Here’s a quick demo..




Conocephalus is a genus of bush-crickets, known as coneheads:


Now I have one beautifully rendered in 3D by Boldport. And unlike the live video above, it chirps in response to light.

The Kit


Qty Item
1x 1W 8Ω 13mm speaker, Multicomp MCKP1330SP1-4723
1x Phototransistor, Everlight PT333-3C
1x Hex Schmitt trigger inverter, ON Semi MC74HC14ADR2G
1x 47µF electrolytic capacitor, Multicomp MCUMR6V3476M4X5
1x 1µF ceramic capacitor, Suntan TS170R1H105MSBFA0R
2 0.1µF ceramic capacitor, Multicomp MC0805B104K500A2.54MM
1x 0.01µF ceramic capacitor, Suntan TS170R2A103KSBBA0R
12 x 4.7KΩ resistor, Multicomp MCF 0.25W 4K7
1x 220Ω resistor, Multicomp MCRE000029
1x 2032 battery holder, Linx BAT-HLD-001
1x Small signal diode, Diotech 1N4148
1x SPST switch, Apem IKD0103101
16cm 20AWG wire

I really appreciate the care and attention that obviously goes into selecting parts. In this kit, the speaker is particularly impressive - it even has an adhesive outer ring for securing to the PCB.


Chirp Circuit

Full details are available Boldport Conehead page, but I redrew the circuit to get a better understanding of how it works …


We basically have three oscillators comprising an RC circuit and Schmitt trigger inverter. These contribute three components to the “chirp”:

  • low-frequency on/off gate
  • audible frequency carrier
  • modulation frequency to add “texture”

This is not pure FM synthesis, as the carrier and modulation circuits do interact. Boldport made this simulation of the circuit:


Pure Data Chirp Model

Boldport projects never fail to inspire some new learning. In the case it introduced me to Pure Data - a pretty amazing open source visual programming language for multimedia.

I reproduced the chirp.pd model and added a few more controls to make it easier to play around with. Here’s a quick example of the sounds produced with different settings:


Here are some settings that simulate the Conehead chirp:

  • 428 gate frequency
  • 8000 carrier frequency
  • 110 modulation frequency
  • 714 modulation amount


The Build





Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.